This invention relates to filter cartridges for drinking water treatment systems, and more specifically to a button for establishing a nonsolvent, physical and sealed connection between a septum and an outlet stack in a water treatment cartridge.
This invention deals with a water treatment cartridge of the type disclosed in U.S. Pat. Nos. 4,857,189 and RE 34,031, both of which are incorporated by reference herein. These cartridges disclose a precoat style of filtration where the treated, activated carbon media filters the water, and in so doing adheres to a bag-like, porous filter septum located in the cartridge. As water enters an inlet to the cartridge and proceeds through an inlet passage, it moves through the filter media, then through the septum and out through an outlet stack and an outlet port. To establish fluid communication between the septum and the outlet stack, a button is used. The button contains a first tubular portion having a throughbore, and a second portion connected to the first portion and having a radially projecting flange with an edge and a diameter.
The flange is configured to be attached to the inside of the septum. A washer is then slid over the first portion and abuts the outside of the septum. Then, using a chemical solvent-type adhesive such as methyl ethyl ketone (MEK) to hold the washer through the layers of the septum against the flange, the washer and flange are bonded. The first portion of the button is press fit into the outlet stack and is then secured with a chemical adhesive to the outlet stack to ensure the connection. The preferred chemical adhesive is a mixture of MEK and ABS and is commercially available under the designation Weld On 3039, made by Industrial Polychemical Co. of Gardenia, Calif., as well as SP-412 ABS Cement, made by C.P. Moyen Co. of Skokie, Ill.
Alternatively, a suitable mixture of this adhesive is made by pouring 1 gallon of the MEK into a container and mixing in 7.5 pounds of scrap ABS. After the mixture has stood for about 12 hours and softened, it is stirred into an even texture and placed in a covered container. This mixture ensures a physical as well as a sealed connection. Establishing a sealed connection is important because the water must go through the button to the outlet stack, and must not seep out.
However, the use of solvent type adhesives such as MEK and the ABS/MEK mixture creates numerous problems in the manufacture and use of the water treatment cartridges. First of all, the adhesives are time consuming to apply, since the processes are done manually. Also, during manufacture, time is needed for the adhesives to dry, further elongating the process. Thus, there is a need for a connection which is easier and less time consuming to assemble during manufacture.
There are also disadvantages to the prior art construction once the cartridge is in use. By using the MEK solvent, there is a concern by some that it might enter into the treated water. Since the purpose of a water filtration of this type is to clean the water, the possibility of the solvent contaminating the water is a problem. Thus, there is also a need for a nonsolvent, sealing connection of the septum to the outlet stack so that the water remains clean of impurities.
Accordingly, an object of this invention is to provide a new and improved button for establishing a positive physical and sealed connection between the septum and the outlet stack.
Another object of this invention is to provide a new and improved button construction which can establish a sealed connection that is easier and less time consuming to assemble during manufacture.
Yet another object is to provide a new and improved button which can establish a sealed connection without the use of chemical solvents.
These and other objects are met or exceeded by the present outlet stack assembly and button, which features a water treatment cartridge that is assembled without the use of solvent. Instead, the present invention utilizes a combination of friction fit and O-rings to provide a positive attachment and seal within the cartridge. In addition to modifying the button, the outlet stack is also specifically dimensioned to facilitate such friction fit and sealed connection.
More specifically, the present water treatment cartridge includes a button for attaching and enabling fluid communication between a septum and an outlet stack of a water treatment cartridge. The septum has an inside, an outside and a plurality of layers. Included in the outlet stack is an opening, a side portion and an annular portion. The button includes a first end with a generally circular portion having a diameter and a plurality of flexible locking members. Opposite the first end on the button is a second end having a generally circular, radially extending flange portion with a diameter and an edge. The flange is configured for attachment to the inside of the septum. Also provided on the button is a central body portion connecting the first and second ends, which has a throughbore and a sealing formation.
On the button, each of the locking members is configured to be inserted into and to abut the annular portion of the outlet stack and is used to attach the button to the outlet stack. To further aid in the attachment of the button to the outlet stack, the locking members are preferably barbs having barb supports. Preferably, adjacent barbs and barb supports are separated by an elongated notch. The configuration of the barbs and barb supports thus eliminates the use of solvent type adhesive (also sometimes referred to below as xe2x80x9csolventxe2x80x9d) or glue during assembly. This eliminates the possibility of contamination, as well as hastening the production process. To further ensure ease of assembly, the barb support has a length which, when combined with the separating notch, is dimensioned so that the barb support is flexible.
To connect the button to the septum, the flange is configured to engage the inside of the septum. Also, there is a washer which abuts the outside of the septum, sandwiching the septum between the washer and the flange. However, instead of using solvent to bond the washer to the flange, the button utilizes friction and at least one radially extending tab which is located on the central portion. The washer is configured such that it frictionally engages the central portion of the button. Also, the tab is located a distance from an end of the central portion sufficient to securely hold a plurality of layers of the septum against the washer. Beads of nonsolvent adhesive glue may be used around the washer to further attach the washer to the septum. This creates a nonsolvent, attachment between the button and the septum. By using only a minimal amount of glue, or no glue at all, the production time can be decreased. Also, since the glue used is nonsolvent, the problem of the water becoming contaminated is eliminated. In another embodiment of the invention, the washer is eliminated, and the button is preferably heat staked to the septum.
Another feature of the present cartridge is that the outlet stack is provided with an axially extending barrel which defines the button-receiving opening. The barrel is dimensioned so that the barbs tightly engage an edge of the barrel. An opposite end of the barrel is contacted by a shoulder on the button so that the button is securely retained in the barrel.
Since the connection must also be sealed to prevent seepage, the central body portion is configured for establishing a sealed connection between said button and the outlet stack. In the preferred embodiment of the invention, the sealed connection is created by the use of an O-ring, which fits into the annular groove. The O-ring creates a sealed connection, which eliminates any seepage of the water through the button.